Installations for reprocessing irradiated nuclear fuels have what are referred to as hot large-area cells for accommodating the process engineering components. In such radiation-shielded cells, the process components are set up in frame structures or support assemblies commonly referred to as racks.
Maintenance operations within the large-area cell which is charged with radioactive radiation are carried out by means of movable remote manipulating machines. The process components which are arranged in the racks are connected together with conduits and are connected to conduits which lead through the cell wall. When the process components are replaced, the conduits must be separated by remote control and re-connected together after a new process component has been installed. Generally, in order to permit such operation of replacing a process component or also dismantling of a rack, it is necessary for entire portions of the conduits to be removed because they would impede replacement of the process component or removal of the rack or of a rack module.
Therefore, use is made of removable conduit parts referred to as conduit connecting units, which at their ends are connected with couplable end flanges. Those end flanges are the flanges which, when joining stationary conduits which pass through the cell wall, are coupled to the end flanges thereof, or are coupled to the end flanges of a conduit connection of a process component which is disposed in the rack. Therefore, a conduit connecting unit is mounted under remote control between the two end flanges of two stationary conduit connections, and is replaceable or removable. The pairs of flanges each including two end flanges are connected by known means such as threaded fasteners or clamping ring coupling assemblies.
When fitting a conduit connecting unit, the end flanges which are to be coupled must be brought together in a centered relationship. Centering aids of that kind are known and are suitable for ensuring that, when the flanges of a pair of flanges are brought together and fastened in the assembled condition, under remote control, the positions of the respective corresponding bores of the end flanges which are to be connected together are in aligned relationship.
As this operation of bringing the pairs of flanges together must be carried out by a remotely-controlled manipulation procedure, a particular problem is presented for the operator who monitors and performs the connecting operation by means of television pictures. It is found that it is difficult to see into the coupling location shortly before the end flanges come together. That results in frequent failures in attempting to install the removable or replaceable conduit connecting unit.
Usually, the end flanges of the conduit connecting unit have threaded fasteners which are held therein so that they cannot be lost and which must be screwed into the end flange of the stationary conduit after the arrays of bores in the two end flanges to be joined have been brought into alignment. It is therefore necessary to maintain the position of the threaded bores in the end flange relative to the through bores (or the threaded fasteners disposed therein) in the end flange of the conduit connecting unit until the oppositely disposed flanges are correctly fastened together by the threaded fasteners, the end flange of the conduit connecting unit being fitted into position by remote control.
It is known for pairs of flanges in nuclear processing installations to be fitted with what are referred to as pilot or registration pins. More specifically, a centering pin is screwed into the shoulder portion of the end flange on the conduit connecting unit, while the tip of the centering pin, which projects out of the above-mentioned end flange, projects into a corresponding centering bore in the other end flange when the two end flanges are brought together. When working with conduit connecting units of unfavorable geometry, for example, a conduit assembly having a configuration with complicated bends, the use of that centering pin gives little advantage and very easily results in faults or damage to the seals of the flanges.
Published German Patent Application DE-OS 33 41 044 which corresponds to copending U.S. patent application Ser. No. 663,444, filed Oct. 22, 1984, discloses a centering device for the remote-controlled coupling of an end flange of a stationary conduit to an end flange of a conduit connecting unit. This centering device is configured so that a vertical centering pin is arranged to project upwardly on the stationary conduit; whereas, a receiving portion having centering surfaces and which fits onto the centering pin is mounted on the removable conduit connecting unit. With this device, an optical aid is provided for bringing together the flanges which are to be coupled to each other.